This invention relates generally to hollow stem augers for drilling a hole in the earth, sometimes several hundred feet deep, and keeping the hole open for other operations such as core sampling, ground water sampling, etc. Typically, the total auger length is formed by a plurality of tubular auger sections, each about five feet long, telescopically connected together at their adjacent ends by a drive shank and socket coupling assembly for transmission of rotary torque. Various lock devices have been used to lock the telescoping shank and socket ends of adjacent auger sections against axial separation, the most common type being a dog-point lock screw, such as screw 40a shown in U.S. Pat. No. 3,190,377 or Acker Drill Company lockscrew Part No. 130365. A screw of this type threads transversely through a tapped hole in the wall of the tubular socket end and has a dog-point that seats within an aligned drilled hole in the tubular shank end. These lockscrews function well when parts are new and clean. However, after use under corrosive, dirty, and abrasive conditions, the lockscrews frequently are frozen in place and difficult to remove when trying to separate the auger sections as they are withdrawn from the hole. The threads on the screw and in the wall of the auger section often become rusted and coated with dirt, and as the screw is turned in or out the threads in the tapped hole are damaged, and often destroyed, thus reducing the useful life of the auger section.
An alternative type of lock device is illustrated in U.S. Pat. No. 3,796,448. While this device addresses the problem of fluid leakage in the area of the coupling joint, it has not been totally successful in keeping water and debris out of the lock pin area and is not sturdy enough to withstand the heavy vibration and tortion loads produced during the drilling operation.